Coating composition of an acrylic polymer containing glycidyl groups and acetoacetoxy groups and an amino ester acrylic polymer

ABSTRACT

A coating composition which cures at ambient temperatures and contains 20-80% by weight of a binder and 80-20% by weight of a solvent for the binder, wherein the binder contains about: 
     A. 60-80% by weight, based on the weight of the binder, of an acrylic polymer A of polymerized monomers of methyl methacrylate and monomers of styrene, alkylmethacrylate and/or alkyl acrylate each having 2-12 carbon atoms in the alkyl group and said polymer having pending from the polymer backbone aminoester groups, hydroxy aminoester groups or hydroxyamine groups, 
     B. 20-40% by weight, based on the weight of the binder, of an acrylic crosslinking polymer B of polymerized monomers of at least 3% by weight, based on the weight of the crosslinking polymer, of a glycidyl constituent of glycidyl methacrylate or acrylate, at least 5% by weight, based on the weight of the crosslinking polymer, of an alkyl methacrylate or acrylate having a pendent group of the formula ##STR1##  and the remainder of the monomers are alkyl methacrylate an acrylate each having 1-12 carbon atoms in the alkyl group; the composition is useful as an exterior finish for automobiles and trucks and for repairing and finishes of automobiles and trucks.

BACKGROUND OF THE INVENTION

This invention is related to a coating composition and in particular toa coating composition that cures rapidly at ambient temperatures to forma finish with improved initial properties such as moisture resistanceand tape marking resistance.

There are a number of coating compositions available for finishing andrepairing of the exterior finish of automobiles and trucks. Thesecompositions cure at ambient temperatures and provide finishes with goodphysical properties such as gloss, hardness, weatherability, goodadhesion, chip resistance and the like. Typical useful compositions areshown in DenHartog et al U.S. Pat. No. 4,525,521 issued June 25, 1985;however, it would be very desirable if these compositions would have afaster initial curing rate without a sacrifice of any of the other veryacceptable properties of the compositions. Other useful compositions areshown in Crawley et al U.S. Pat. No. 4,131,571 issued Dec. 26, 1978,Miller U.S. Pat. No. 4,020,216 issued Apr. 26, 1977, Miller U.S. Pat.No. 3,844,993 issued Oct. 29, 1974, Miller U.S. Pat. No. 3,789,037issued Jan. 29, 1974 and Vasta U.S. Pat. No. 3,558,564 issued Jan. 26,1971. These compositions contain isocyanate compounds to achieve curingand excellent properties. It would be desirable to provide an ambienttemperature curing composition that has a rapid initial curing rate,excellent physical properties, acceptable "pot life" and does notcontain an isocyanate compound.

The novel composition of this invention has a rapid initial cure rate,i.e., crosslinks quickly at ambient temperatures and provides excellentinitial properties such as moisture and tape marking resistance, has anacceptable pot life, forms a finish with excellent durability and hasthe other properties that are necessary for exterior finishes forautomobiles and trucks and does not contain an isocyanate compound.

SUMMARY OF THE INVENTION

A coating composition containing about 20-80% by weight of a binder and80-20% by weight of a solvent for the binder, wherein the bindercontains about:

A. 60-80% by weight, based on the weight of the binder, of an acrylicpolymer A of polymerized monomers of methyl methacrylate and monomersselected from the group of styrene, alkyl methacrylate and alkylacrylate each having 2-12 carbon atoms in the alkyl group and thepolymer has pending from the carbon-carbon atoms of the polymer backboneaminoester groups of the formula ##STR2## where R is an alkylene grouphaving 2-3 carbon atoms; or hydroxy aminoester groups of the formula##STR3## groups of the formula ##STR4## where R¹ is an alkyl group of1-8 carbon atoms; and B. 20-40% by weight, based on the weight of thebinder, of an acrylic crosslinking polymer B of polymerized monomers ofat least 3% by weight, based on the weight of the crosslinking polymer,of a glycidyl constituent selected from the group of glycidylmethacrylate and glycidyl acrylate, and at least 5% by weight of analkyl acrylate or methacrylate having a pendent group of the formula andthe remainder of the monomers are ##STR5## selected from the group ofalkyl methacrylate and alkyl acrylate each having 1-12 carbon atoms inthe alkyl group;

wherein polymers A and B each have a weight average molecular weight ofabout 5,000-40,000 determined by gel permeation chromatography usingpolymethyl methacrylate as a standard.

DETAILED DESCRIPTION OF THE INVENTION

The coating composition contains about 20-80% by weight of a filmforming binder and 80-20% by weight of solvent for the binder. Thebinder is a blend of about 60-80% by weight of acrylic polymer A and20-40% of acrylic crosslinking polymer B. The composition can be used asa clear finish without pigments or only lightly pigmented whileretaining its clear characteristics or can be pigmented and used as aconventional monofinish or as the color coat of a color coat/clear coatfinish. Typically, a pigment to binder weight ratio of about 1:100 to200:100 can be used.

Both acrylic polymer A and acrylic crosslinking polymer B have a weightaverage molecular weight of about 5,000-40,000 and a number averagemolecular weight of about 2,000-15,000. Molecular weight is determinedby gel permeation chromatography using polymethyl methacrylate as thestandard.

One method for preparing the acrylic polymer A is to polymerize monomersof methyl methacrylate, alkyl methacrylate, alkyl acrylate or mixturesthereof, each having 2-12 carbon atoms in the alkyl group, andmethacrylic acid or acrylic acid. Styrene also can be used in amounts ofabout 50% by weight of the polymer. The carboxyl groups of the resultingpolymer are reacted with an alkylene imine preferably in a molar ratioof about 1:1 to form pendent amino ester groups from the backbone of thepolymer.

The polymerization of the monomers to form the acrylic polymer A iscarried out by conventional techniques in which the monomers, solventsand polymerization catalysts are charged into a polymerization vesseland reacted at about 50-175C for about 0.5-6 hours to form the polymer.

Typical solvents used are toluene, xylene, ethyl acetate, acetone,methyl ethyl ketone, methyl isobutyl ketone, ethanol, isopropanol andother aliphatic, cycloaliphatic and aromatic hydrocarbon esters, ethers,ketones and alcohols as are conventionally used.

One preferred acrylic polymer contains about 20-30% by weight methylmethacrylate, 25-35% by weight of an alkyl methacrylate having 4-12carbon atoms in the alkyl group such as butyl methacrylate, 30-40%styrene and 10-15% by weight methacrylic acid. The carboxyl groups ofthe polymer are post reacted with an alkylene imine such as propyleneimine, preferably in a 1:1 molar ratio, to a provide amino ester groupspendent from the carbon-carbon polymer backbone of the formula ##STR6##where R is an alkylene group having 2-3 carbon atoms.

Other useful acrylic polymers are the aformentioned acrylic polymersexcept that the aminoester group is replaced by hydroxy aminoestergroups of the formula ##STR7## Such polymers are disclosed in DenHartoget al. U.S. Pat. No. 4,525,521 issued June 25, 1985 which is herebyincorporated by reference.

Another useful type of acrylic polymer are the aforementioned acrylicpolymers except that the aminoester group is replaced with groups of theformula ##STR8## where R¹ is an alkyl group of 1-8 carbon atoms. Suchpolymers are disclosed in Snow U.S. Pat. No. 4,785,054 issued Nov. 15,1988 which is hereby incorporated by reference.

The acrylic crosslinking polymer B is composed of polymerized monomersof at least 3% by weight of a glycidyl constituent which is eitherglycidyl methacrylate or glycidyl acrylate and at least 5% by weight ofan alkyl methacrylate or acrylate having 1-4 carbon atoms in the alkylgroup and pendent groups of the formula ##STR9## and the remainder ofthe monomers are alkyl methacrylate, alkyl acrylate or mixtures thereofwhere the alkyl group contains 1-12 carbon atoms.

Acetoacetoxy ethyl methacrylate or acetoacetoxyethyl acrylate aretypically useful and preferred monomers that contain the aforementionedpendent group.

The acrylic crosslinking polymer can also be formed by preparing ahydroxyl containing acrylic polymer and reacting the hydroxyl groups ofthe polymer with a diketene or with an alkylate of acetoacetic acid suchas methyl acetoacetate or t-butyl aceto acetate. A blocked ketene suchas 2,2,6 trimethyl-4H-1,3 dioxin-4- one may also be used.

Useful acrylic crosslinking polymers are composed of polymerizedmonomers of about 3-80% by weight, based on the weight of the polymer,of glycidyl methacrylate or acrylate, 15-40% by weight, based on theweight of the polymer of an alkyl methacrylate having 1-12 carbon atoms,preferably 4-12 carbon atoms, in the alkyl group such as butylmethacrylate and 3-57% by weight, based on the weight of the polymer ofacetoacetoxy ethyl methacrylate.

The following are examples of preferred acrylic crosslinking polymers:

45% glycidyl methacrylate/40% butyl methacrylate/15% acetoacetoxy ethylmethacrylate,

50% glycidyl methacrylate/40% butyl methacrylate/10% acetoacetoxy ethylmethacrylate,

55% glycidyl methacrylate/40% butyl methacrylate/5% acetoacetoxy ethylmethacrylate.

Other useful acrylic crosslinking are as follows:

30% glycidyl methacrylate/40% butyl methacrylate/30% acetoacetoxy ethylmethacrylate,

3% glycidyl methacrylate/40% butyl methacrylate/57% acetoacetoxy ethylmethacrylate.

The aforementioned percentages are weight percentages.

It was found that when only acetoacetoxy ethyl methacrylate or acrylatewas used in the acrylic crosslinking polymer, the "pot life" of thecomposition was unacceptably short and finishes of the composition hadunacceptable moisture and acid resistance after application and curing.With only the presence of the glycidyl component, the coatings earlycure properties (24 hours cure at ambient temperatures) needed to beimproved e.g. hardness tape print resistance and moisture resistance. Bybalancing the amount of acetoacetoxy ethyl methacrylate or acrylate andthe glycidyl component in the crosslinking polymer, a composition wasformed that had an adequate "pot life" and provided a finish that hadexcellent durability, weatherability, hardness, tape print resistance,appearance properties such as gloss and distinctness of image and hadacceptable yellowing performance.

Typical alkyl methacrylate and alkyl acrylate monomers that are used toprepare the aforementioned polymers are ethyl methacrylate, propylmethacrylate, butyl methacrylate, isobutyl methacrylate, pentylmethacrylate, hexyl methacrylate, ethyl hexyl methacrylate, nonylmethacrylate, decyl methacrylate, lauryl methacrylate, ethyl acrylate,propyl acrylate, butyl acrylate, isobutyl acrylate, pentyl acrylate,hexyl acrylate, ethyl hexyl acrylate, nonyl acrylate, decyl acrylate,lauryl acrylate and the like.

About 0.1-4% by weight, based on the weight of the binder, of a catalystcan be added to the coating composition. Typical catalysts areresorcinol, resorcinol monobenzoate, boron trifluoride amine complex,phenol, para methoxy phenol, parahydroxy methyl benzoate andhydroquinone.

As mentioned before, the composition can contain pigments. Thesepigments can be introduced into the composition by first forming a millbase with the acrylic polymer utilized in the composition or with othercompatible polymers or polymer dispersants by conventional techniques,such as sand-grinding, ball milling, attritor grinding, two roll millingto disperse the pigments The mill base is blended with the film-formingconstituents as shown in the following Examples.

Any of the conventional pigments used in coating compositions can beutilized in the composition such as the following: metallic oxides, suchas titanium dioxide, zinc oxide, iron oxide and the like, metalhydroxide, metal flakes such as aluminum flake, chromates, such as leadchromate, sulfides, sulfates, carbonates, carbon black, silica, talc,china clay, phthalocyanine blues and greens, organo reds, organomaroons, pearlescent pigments and other organic pigments and dyes.

To improve weatherability of finishes of the coating composition about0.1-5%, by weight, based on the weight of the binder, of an ultravioletlight stabilizer or a combination of ultraviolet light stabilizers canbe added. Typically useful ultra-violet light stabilizers are disclosedhereinafter.

The coating composition of this invention can be applied over a varietyof substrates, such as metal, glass, plastic, reinforced plastic and thelike, by any of the conventional application methods, such as spraying,electro-static spraying, dipping, brushing, flow-coating and the like.The viscosity of the composition can be adjusted for any of thesemethods by adding solvents if necessary. Generally, the composition isutilized at a high solids content which keeps air pollution at a minimumlevel.

The coatings are usually dried at ambient temperatures and are tack freeafter about 1-4 hours and fully cured after about 4-7 days. The coatingscan be baked at relatively low temperatures of about 65 °-140°C. forabout 15 minutes-2 hours. The resulting coating is about 0.1-5 milsthick but for most uses, a 1-3 mil thick coating is used. One techniquethat is used to insure that there will be no popping or cratering of thecoating is to allow the solvents to flash off for at least 2 minutesbefore a second coating is sprayed on or otherwise applied, then waitingabout 2-10 minutes before baking the coating to allow any residualsolvents to flash off if the coating is to be baked. The resultingcoating has good gloss and can be rubbed or polished with conventionaltechniques to improve the smoothness, appearance and gloss. The coatinghas good adhesion to substrates of all types, is hard and resistant toweathering, solvents, alkali, scratches and the like. Thesecharacteristics make the composition particularly useful as a finish forautomobiles, trucks, airplanes, railroad equipment and for the repair offinishes of trucks and automobiles.

Another aspect of this invention is to utilize the composition as aclear coat/color coat finish for substrates. In this finish, a clearcoat top layer is in firm adherence to a color coat layer that is inadherence with a substrate. The clear coat is a transparent film of thecoating composition of this invention and the color coat is the coatingcomposition of this invention and contains pigments in apigment-to-binder ratio of about 1/100 to 150/100 and other additives.

The thickness of the fully cured color coat and clear coat can vary.Generally, the color coat is about 0.4-1.5 mils thick and preferably0.6-1.0 mils thick and the clear coat is about 0.5-6.0 mils thick andpreferably 0.8-2.0 mils thick. Any of the aforementioned conventionalpigments can be used in the color coat including metallic flake pigmentscan be used. The clear coat can also contain transparent pigments, i.e.,pigments having the same or similar refractive index as the binder ofthe clear coat and are of a small particle size of about 0.015-50microns. Typical pigments that can be used in a pigment-to-binder weightratio of about 1/100 to 10/100 are inorganic silioeous pigments, such assilica pigments. These pigments have a refractive index of about1.4-1.6.

To form a durable finish, the clear coat and optionally, the color coatcontain about 0.1-5% by weight based on the weight of the binder, of anultraviolet light stabilizer. Typical ultraviolet light stabilizers thatare useful are as follows:

Benzophenones such as hydroxy dodecyloxy benzophenone, 2,4dihydroxybenzophenone, hydroxybenzophenones containing sulfonic groupsand the like.

Triazoles such as 2-phenyl-4(2',4'-dihydryoxylbenzoyl)-triazoles,substituted benzotriazoles such as hydroxy-phenyltriazoles and the like.

Triazines such as 3,5-dialkyl4-hydroxyphenyl derivatives of triazine,sulfur containing derivatives of diallyl-4-hydroxy phenyl triazines,hydroxy phenyl-1,3,5-triazine and the like.

Benzoates such as dibenzoate of diphenylol propane, tertiary butylbenzoate of diphenylol propane, and the like.

Other ultraviolet light stabilizers that can be used include lower alkylthiomethylene containing phenols, substituted benzenes such as1,3-bis(2'-hydroxybenzoyl)benzene, metal derivatives of3,5-di-t-butyl-4-hydroxy phenyl propianic acid, asymmetrical oxalicacid, diarylamides, alkylhydroxy-phenyl-thioalkanoic acid ester and thelike.

Particularly useful ultraviolet light stabilizers that can be used arehindered amines of bipiperidyl derivatives such as those in Murayama etal., U.S. Pat. No. 4,061,616, issued Dec. 6, 1977.

One preferred combination of ultraviolet light stabilizer is abenzotriazole and a hindered amine light stabilizer and is preferablyused in a weight ratio of about 1:1. The combination is used in anamount of about 1-4% by weight, based on the weight of the binder. Onepreferred benzotriazole is "Tinuvin" 328,2-(2 hydroxy-3,5-ditertiaryamyl-phenol)-2H-benzotriazole and a preferred hindered amine is"Tinuvin" 292, bis(1,2,2,6,6-pentamethyl-4 piperidinyl)sebacate. Anotherpreferred hindered amine is "Tinuvin" 770, di[4(2,2,6,6 tetramethylpiperdinyl)]sebacate.

The clear coat/color coat finish is applied by conventional sprayingtechniques and preferably the clear coat is applied to the color coatwhile the color coat is still wet. Other conventional applicationtechniques can be used such as brushing, roller coating, electrostaticspraying the the like. The finish is then dried at ambient temperaturesor can be used as indicated above.

The following Examples illustrate the invention. All parts andpercentages are on a weight basis unless otherwise indicated. Molecularweights are determined by gel permeation chromatography using polymethylmethacrylate as the standard.

EXAMPLE 1

Acrylic polymer A solution was prepared by charging the followingconstituents into a reaction vessel equipped with a heating mantle,reflux condenser, thermometer and stirrer:

    ______________________________________                                                             Parts by Weight                                          ______________________________________                                        Portion 1                                                                     Butyl acetate          959.53                                                 Toluene                367.08                                                 Isopropanol            641.24                                                 Butyl methacrylate monomer (BMA)                                                                     127.22                                                 Portion 2                                                                     Butyl methacrylate monomer                                                                           817.23                                                 Methyl methacrylate monomer (MMA)                                                                    755.55                                                 Styrene monomer (S)    1066.42                                                Methacrylic acid monomer (MAA)                                                                       329.93                                                 Portion 3                                                                     2,2'-Azobis(methylbutyronitrile)                                                                      97.58                                                 Toluene                295.06                                                 Portion 4                                                                     Methacrylic acid monomer                                                                              48.81                                                 Toluene                148.69                                                 Portion 5                                                                     2,2'-Azobis(methylbutyronitrile)                                                                      1.17                                                  Toluene                 12.77                                                 Portion 6                                                                     Butyl acetate          2160.71                                                Portion 7                                                                     Propylene imine        251.01                                                 Total                  8080.00                                                ______________________________________                                    

Portion 1 is charged into the reaction vessel and mixed and theresulting mixture is heated to its reflux temperature of about 90C.Portion 2 is premixed and slowly added at a uniform rate over a 90minute period to the reaction vessel while maintaining the mixture atits reflux temperature. Portion 3 is premixed and fed into the reactionvessel simultaneously with Portion 2 over the same time period.Immediately after Portions 2 and 3 have been added Portion 4 is addedover a 45 minute period while holding the reaction mixture at its refluxtemperature and then holding the reaction mixture at its refluxtemperature for an additional 30 minutes. Portion 5 is added and thenthe reaction mixture is held at its reflux temperature for 45 minutes.Portion 6 is added and the reaction mixture is cooled to 60C and thenPortion 7 is added and the reaction mixture is heated to its refluxtemperature and held at this temperature until and acid no. of 2 isreached.

The resulting polymer solution has a polymer weight solids content ofabout 42%, a Gardner Holdt viscosity at 25C of about C +1/2to D +1/2.The polymer has a composition of about 24% methyl methacrylate, 30%butyl methacrylate, 34% styrene and 12% methacrylic acid postiminatedwith propylene imine. The resulting polymer has an acid no. of about 2,a number average molecular weight of about 6,800 and a weight averagemolecular weight of about 10,600.

Four crosslinking polymer solutions were prepared. The polymer ofcrosslinking polymer solution 1 did not contain acetoacetoxy ethylmethacrylate (AAEM) and is the control. Crosslinking polymer solutions2,3 and 4 contained acetoacetoxy ethyl methacrylate in the followingamounts of 15%, 10% and 5% as shown in the following table:

    ______________________________________                                        Crosslinking                                                                  Polymer    % BMA       % GMA    % AAEM                                        ______________________________________                                        1          40          60        0                                            2          40          45       15                                            3          40          50       10                                            4          40          55        5                                            ______________________________________                                    

Crosslinking polymer solution 1 was prepared by charging the followingingredients into a reaction vessel equipped as above:

    ______________________________________                                                              Parts by weight                                         ______________________________________                                        Portion 1                                                                     Butyl acetate           1489.26                                               Toluene                  255.11                                               Ethyl acetate            413.87                                               Portion 2                                                                     Glycidyl methacrylate monomer (GMA)                                                                   2331.23                                               Butyl methacrylate monomer (BMA)                                                                      1554.08                                               Portion 3                                                                     Butyl acetate            560.34                                               2,2'-Azobis(methylbutyronitrile)                                                                       186.78                                               Portion 4                                                                     Butyl acetate            143.22                                               2,2'-Azobis(methylbutyronitrile)                                                                       47.74                                                Portion 5                                                                     Butyl acetate           1020.01                                               Propylene glycol monomethyl acetate                                                                    483.20                                               Total                   8484.84                                               ______________________________________                                    

Portion 1 was charged into a reaction vessel and heated to its refluxtemperature of about 110-112 C. Portions 2 and 3 are each premixed andsimultaneously added to the reaction vessel with constant stirring overa 2 hour period while maintaining the resulting reaction mixture at itsreflux temperature. Immediately after portions 2 and 3 were added,Portion 4 was added over a 30 minute period and the reaction mixture washeld at its reflux temperature for an additional 30 minutes. Portion 5was added and the reaction mixture was cooled to room temperature.

The resulting polymer solution had a polymer solids of about 46% and arelative viscosity of about 1.037-1.039. The composition of the polymerswas 40% butyl methacrylate and 60% glycidyl methacrylate and had anumber average molecular weight of about 2410 and a weight averagemolecular weight of about 5250.

Crosslinking polymer solution 2 was prepared by charging the followingconstituents into a reaction vessel described above:

    ______________________________________                                                             Parts by Weight                                          ______________________________________                                        Portion 1                                                                     Butyl acetate          745.00                                                 Toluene                128.00                                                 Ethyl acetate          207.00                                                 Portion 2                                                                     Glycidyl methacrylate monomer                                                                        875.00                                                 Butyl methacrylate monomer                                                                           777 00                                                 Acetoacetoxy ethyl methacrylate monomer                                                              291.00                                                 Butyl acetate          280.00                                                 2,2'-Azobis(methylbutyronitrile)                                                                      93.00                                                 Portion 3                                                                     Butyl acetate           72.00                                                 2,2'-Azobis(methylbutyronitrile)                                                                      24.00                                                 Portion 4                                                                     Butyl acetate          510.00                                                 Propylene glycol monomethyl acetate                                                                  242.00                                                                  Total 4244.00                                                ______________________________________                                    

Portion 1 was charged into the reaction vessel and heated to its refluxtemperature. Portion 2 was premixed and added at a uniform rate over a 2hour period while maintaining the reaction mixture at its refluxtemperature. Immediately after portion 2 was completely added, Portion 3was added over a 30 minute period and then the reaction mixture was heldat its reflux temperature for an additional 30 minutes. Portion 4 wasadded and the reaction mixture was cooled to room temperature.

The resulting polymer solution had a polymer solids of about 46%. and aGardner Holdt viscosity of about A. The composition of the polymers is40% butyl methacrylate, 45% glycidyl methacrylate and 15% acetoacetoxyethyl methacrylate and had a number average molecular weight of about1,976 and a weight average molecular weight of about 5,303.

Crosslinking polymer solutions 3 and 4 were prepared using the aboveprocedure and constituents except the monomer amounts were adjusted toprovide the following compositions:

Crosslinking polymer solution 3 - polymer solids 46%, Gardner Holdtviscosity -A, polymer composition 40% butyl methacrylate, 50% glycidylmethacrylate, 10% acetoacetoxy ethyl methacrylate; number averagemolecular weight - 2,650, weight average molecular weight 5,502.

Crosslinking polymer solution 4 - polymer solids 46%, Gardner Holdtviscosity -A, polymer composition 40% butyl methacrylate, 55% glycidylmethacrylate, 5% acetoacetoxy ethyl methacrylate; number averagemolecular weight - 2,577, weight average molecular weight 5,377.

A Clear Polymer Solution was prepared by blending the followingconstituents:

    ______________________________________                                                             Parts by Weight                                          ______________________________________                                        Acrylic polymers A solution (prepared                                                                456.51                                                 above)                                                                        Isopropanol            9.86                                                   Propylene glycol monoethyl ether acetate                                                             31.86                                                  Hydrocarbon solvent    10.50                                                  Mineral spirits (aromatic controlled)                                                                10.61                                                  UV Stabilizer ("Tinuvin" 328)                                                                        2.72                                                   HALS light stabilizer ("Tinuvin" 292)                                                                2.72                                                   Flow control agent ("Acrylon" MFPF from                                                              0.39                                                   Synthron)                                                                     Slip agent (BYK 325)   0.53                                                   Non-Aqueous Dispersion Rheology                                                                      12.85                                                  Control Agent                                                                 Total                  538.55                                                 A Solution was prepared by blending the                                       following constituents:                                                       Propylene glycol monoethyl ether acetate                                                             30.78                                                  Hydrocarbon solvent    26.69                                                  Ethyl 3-ethoxy propionate                                                                            59.56                                                  Butyl Cellosolve Acetate                                                                             1.12                                                   Catalyst solution (p-hydroxymethyl                                                                   7.74                                                   benzoate)                                                                     Total                  125.89                                                 ______________________________________                                    

Clear coating compositions 1,2,3 and 4 were each prepared by mixing67.38 parts of the above prepared Clear Polymer Solution, 15.78 parts ofthe above Solution and 16.84 parts of the respective CrosslinkingPolymer Solutions 1,2,3, and 4 together. Each clear coating compositionwas sprayed onto separate primed steel panel coated with an acryliclacquer pigmented finish and then cured for about 168 hours at roomtemperature. In each case, the resulting clear finish was about 2 milsthick. Each panel was tested for tape print resistance and for waterspot resistance.

In the tape print resistance test masking tape was applied every 4 hoursduring a period of 8-24 hours after application of the finish. The tapewas removed one hour after it was applied and then 1 hour after the tapewas removed, the finish was inspected for printing resulting from thetape. The time at which no printing from the tape was noted is shownbelow.

In the water spot resistance test, three drops of distilled waster wereapplied every 4 hours after application of the finish and the water wasallowed to evaporate. After the water evaporated the panel was inspectedfor distortion of the finish. The time at which no distortion from waterwas noted is shown below.

    ______________________________________                                                          Tape Print  Water Spot                                      Test              Resistance (1)                                                                            Resistance (2)                                  ______________________________________                                        Coating Comp. 1 (control)                                                                       16 hours    20 hours                                        Coating Comp. 2 (15% AAEM)                                                                       8 hours     8 hours                                        Coating Comp. 3 (10% AAEM)                                                                      12 hours    12 hours                                        Coating Comp. 4 (5% AAEM)                                                                       16 hours    12 hours                                        ______________________________________                                         (1)Time in hours when tape did not imprint finish.                            (2)Time in hours when water did not spot finish.                         

Other properties of the each of the finishes were tested such as gloss,distinctness of image, durability, chemical resistance and adhesion andwere acceptable for an automotive quality finish.

We claim:
 1. A coating composition comprising 20-80% by weight of abinder and 80-20% by weight of a solvent for the binder, wherein thebinder consists essentially of about:A. 60-80% by weight of the binder,of an acrylic polymer A consisting essentially of polymerized monomersof methyl metharcrylate and monomers selected from the group consistingof styrene, alkyl metharylate and alkyl acrylate each having 2-12 carbonatoms in the alkyl group and said polymer having pending from thecarbon-carbon atoms of the polymer backbone reactive groups selectedfrom the group consisting of aminoester groups of the formula ##STR10##where R is an alkylene group having 2-3 carbon atoms, hydroxyaminioester groups of the formula ##STR11## groups of the formula ##STR12##where R¹ is an alkyl group of 1-8 carbons atoms; and B. 20-40% byweight, based on the weight of the binder, of an acrylic crosslinkingpolymer B consisting essentially of polymerized monomers of at least 3%by weight, based on the weight of the crosslinking polymer, of aglycidyl constituent selected from the group consisting of glycidylmethacrylate and glycidyl acrylate, at least 5% by weight of an alkylacrylate or alkyl methacrylate having a pendent group of the formula##STR13## and the remainder of the monomers being selected from thegroup consisting of alkyl methacrylate and alkyl acrylate each having1-12 carbon atoms in the alkyl groups;wherein said polymers A and B eachhave a weight average molecular weight of about 5,000-40,000 determinedby gel permeation chromatography using polymethyl methacrylate as astandard.
 2. The coating composition of claim 1 containing pigments in apigment-to-binder weight ratio of 1:100 to 200:100.
 3. The coatingcomposition of claim 1 in which the acrylic polymer A consistsessentially of polymerized monomers of methyl methacrylate and monomersselected from the group consisting of styrene, alkyl methacrylate andalkyl acrylate, each having 2-12 carbon atoms in the alkyl group andsaid polymer having pending from the carbon-carbon atoms of the polymerbackbone reactive aminoester groups of the formula ##STR14## where R isan alkylene group having 2-3 carbon atoms.
 4. The coating composition ofclaim 3 in which the acrylic polymer A consists essentially of about20-30% by weight, based on the acrylic polymer, of methyl methacrylate30-40% by weight, based on the weight of the acrylic polymer, ofstyrene,, 25-35% by weight, based on the weight of the acrylic polymer,of an alkyl methacrylate having 4-12 carbon atoms in the alkyl group and10-15% by weight, based on the weight of the acrylic polymer, ofmethacrylic acid; said polymer reacted with an alkylene imine to providesaid amino ester groups.
 5. The coatings composition of claim 1 in whichthe acrylic polymer A consists essentially of polymerized monomers ofmethyl methacrylate and monomers selected from the group consisting ofstyrene, alkyl methacrylate and alkyl acrylate, each having 2-12 carbonatoms in the alkyl group and said polymer having pending from thecarbon-carbon atoms of the polymer backbone hydroxyaminio ester groupsof the formula ##STR15##
 6. The coating composition of claim 1 in whichthe acrylic polymer A consists essentially of polymerized monomers ofmethyl methacrylate and monomers selected from the group consisting ofstyrene, alkyl methacrylate and alkyl acrylate, each having 2-12 carbonatoms in the alkyl group and said polymer having pending from thebackbone groups of the formula ##STR16## where R¹ is an alkyl group of1-8 carbon atoms.
 7. The coating composition of claim 3 in which theacrylic crosslinking polymer B consists essentially of about 3-80% byweight, bases on the weight of the acrylic crosslinking polymer, ofglycidyl methacrylate, or glycidyl acrylate 15-40% by weight, based onthe weight of the acrylic crosslinking polymer, of an alkyl methacrylatehaving 1-12 carbon atoms in the alkyl group and 3-57 by weight, based onthe weight of the acrylic crosslinking polymer of an alkyl methacrylateor alkyl acrylate each having 1-4 carbon atoms in the alkyl group andeach having a pendent group of the formula ##STR17##
 8. The coatingcomposition of claims 4,5 or 6 in which the acrylic crosslinking polymerB consists essentially of about 3-80% by weight based on the weight ofthe acrylic crosslinking polymer, of glycidyl metharylate, 15-40% byweight, based on the weight of the acrylic crosslinking polymer, of analkyl methacrylate having 4-12 carbon atoms in the alkyl group and 3-57%by weight, based on the weight of the acrylic crosslinking polymer ofacetoacetoxy ethyl methacrylate.
 9. The coating composition of claim 1containing about 0.1-4% by weight, based on the weight of the binder, ofa catalyst selected from the group consisting of resorcinol, resorcinolmonobenzoate, boron trifuloride amine complex, phenol, para methoxyphenol, parahydroxymethyl benzoate.
 10. The coating composition of claim1 containing 0.1-5% by weight, based on the weight of the binder, ofultraviolet light stabilizer.
 11. The coating composition of claim 2 inwhich the binder consists essentially of aboutA. acrylic polymer Aconsists essentially of about 20-30% by weight, based on the acrylicpolymer, of methyl methacrylate, 30-40% by weight, based on the weightof the acrylic polymer, of styrene, 25-35% by weight, based on theweight of the acrylic polymer, of alkyl methacrylate methacrylate having4-12 carbon atoms in the alkyl group and 10-15% by weight, based on theweight of the acrylic polymer, of methacrylic acid; said polymer reactedwith an alkylene imine to provide amino ester groups pendent from thecarbon-carbon polymer backbone of the formula ##STR18## where R is analkylene group having 2-3 carbon atoms; and B. acrylic crosslinkingpolymer B consists essentially of about 3-80% by weight, based on theweight of the acrylic crosslinking polymer, of glycidyl methacrylate,15-40% by weight, based on the weight of the acrylic crosslinkingpolymer, of alkyl methacrylate having 14-12 carbons in the alkyl groupand 5-57% by weight, based on the weight of the acrylic crosslinkingpolymer, of acetoacetoxy ethyl methacrylate.